Generally, various kinds of goods, such as powder-form goods and foodstuffs, are packaged before they are shipped to their respective market, in such a way that the goods are for example, placed in a plastic or aluminum-foil laminated flexible bag, the bag being then sealed and put in a rigid plastic- or cardboard- made outer packaging box or case. Such outer packaging box usually has a design or trademark printed on the exterior thereof and has greater rigidity than the bag so that it also serves as a reinforcement for the bag.
If a sealed flexible bag in which goods are contained is to be received into an outer packaging box having a sectional area of same order as that of the bag, it has to be forcibly pushed into the box. This may sometimes result in the flexible bag breaking on account of friction with the inner surface of the box. To avoid such trouble, it has been a usual practice that the operator put his hands in the opening of the bag to expand the bag into shape, whereupon the bag is inserted into the outer packaging box so that the box and the bag are integrally fitted together, goods being then filled into the bag. In this way it is possible to place into an outer packaging box a bag having a sectional area of same order as that of the box and thereby to effect packaging such that there is no gap between the outer box and the bag at any corner of the box.
However, with such practice that a bag is placed into an outer packaging box while the bag is expanded by hand, the trouble is that the bag does not closely contact the inner surface of the box, there being caused pleat-like lines or bellows-like marks to the bag. Such phenomenon is particularly noticeable at bottom corners of the box and this often results in poor volumetric efficiency.